Automatic screw-driving machine



Dec. 9, 1969 J. H. LARSEN 3,482,512

AUTOMATIC SCREW-DRIVING MACHINE Filed Jan. 26, 1968 v 2 Sheets-Sheet 1 INVENTOR.

I FED] 506W f/LA/QSE/V Dec. 9, 1969 J. H. LARSEN 3,482,612

AUTOMATIC SCREW-DRIVING MACHINE Filed Jan. 26, 1968 I 2 Sheets-Sheet 2 1N VENTOR Jol /v H mess/v BY W Tram/5y United States Patent 3,482,612 AUTOMATIC SCREW-DRIVING MACHINE John H. Larsen, 8800 E. Dalen St., Downey, Calif. 90242 Filed Jan. 26, 1968, Ser. No. 700,789 Int. Cl. B27m 7/00 US. Cl. 144-32 9 Claims ABSTRACT OF THE DISCLOSURE A stand having a post on which a vertically movable carriage is movable between retracted and screw-driving positions, a motor-driven screwdriver bit carried by said carriage, laterally separable jaws having a passage into which said bit extends and connected by links of limited resilience to means that is spring-biased downwardly by said carriage as the same and said bit move downwardly, means carried by the frame to engage between the jaws to separate them when the frame is at each of its extreme positions of movement, and means to feed screws to the lower end of said jaws and operated in timed relation with the movement of the carriage.

BACKGROUND OF THE INVENTION The automatic feeding and driving of screws require precision of operation as well as provision of means that insures against gaps in the feed for whatever reason. Thus, dependability is an important feature. Also, speed of operation is important in that low operating costs follow therefrom. Hence, the invention contemplates a single-stroke operation that successively feeds, sets and drives screws, whether self-tapping or into tapped holes.

The present invention has for its primary object to provide a machine having the above-enumerated attributes.

This invention also has for its objects to provide such means that are positive in operation, convenient in use, easily installed in a working osition and easily disconnected therefrom, economical of manufacture, relatively simple, and of general superiority and serviceability.

SUMMARY OF THE INVENTION The present machine comprises, generally, a support stand 10, a carriage 11 mounted on said stand for vertical movement relative to means or a member 12 disposed on said stand and into holes in which screws S are to be driven, a power screwdriver 13 carried by said carriage and provided with a downwardly directed bit 14, resiliently mounted means 15 supported by the stand and having a compression spring 16 that is engaged by the carriage and imposes a bias on said means in a direction toward the means 12 on the stand, laterally separable jaw means 17 coaxial with the bit 14 and in which screws are received successively, are set in driving position, and are driven by the bit into holes in the member 12, means 18 connecting the jaw means to the resiliently mounted means and movable therewith, means 19 carried by the carriage 11 to engage and laterally separate the jaws means 17 at both the retracted and projected positions of the carriage relative to the member 12, means 20 to feed screws to the jaw means 17 below the lower end of the bit 14, and means 21 to control the operation of said means 20 from the carriage as the same is moved.

The invention also comprises novel details of construction and novel combinations and arrangements of parts, which will more fully appear in the course of the following description, which is based on the accompanying drawings. However, said drawings merely show, and the following description merely describes, preferred embodi- 3,482,612 Patented Dec. 9, 1969 ments of the present invention, which are given by way of illustration or example only.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a broken side elevational view of an automatic screw-driving machine according to the invention.

FIG. 2 is a cross-sectional view as taken on the line 22 of FIG. 1.

FIG. 3 is an enlarged and fragmentary side view of the screw-setting and driving means of the invention.

FIG. 4 is a fragmmentary plan view as taken in the direction of the arrows 4-4 of FIG. 1.

FIG. 5 is a partial rear and partial vertical sectional view of jaw means used in the machine.

FIG. 6 is a plan sectional view as taken on the line 6 of FIG. 3.

FIG. 7 is a vertical sectional view of a modified form of bit.

In the drawings, like reference characters designate similar parts in the several views.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The support stand 10 is shown as having a base 25 with a support surface 26 for the member or means 12, and a vertical post 27 extending from the rear portion of said base 25. It will be clear that other positions of the post may be employed for particular conditions where the movement of screws to and during driving thereof is changed.

The carriage 11 is shown as a frame 28 provided with spaced slide bearings 29 and 30 engaged with the post 27 and a forward extension 31 formed as a clamp to fixedly mount the screwdriver 13 on said carriage. An adjustable stop 32 on said post provides means to limit the retracted position of the carriage, and a stop 33 on said post and provided with an adjustment screw 34 provides means that accurately limit the projected movement of the carriage. An adjustable bracket 35 is shown as affixed to the post 27 below the stop 33, the same constituting the support for the means 15.

Movement of said carriage 11 is effected by means comprising a gear 36 mounted on the stop 32, a gear rack 37 engaged with said gear and affixed to the frame 28 of the carriage, and an operating arm 38 on the axis of said gear. It will be clear that clockwise movement of said arm 38 will cause downward movement of the carriage. Release of the arm will allow the spring 16, which is engaged with the lower edge of the frame 28, to return the carriage to the position shown with the stop 32 limiting said return movement.

The member or means 12 is not part of the machine but merely any work or workpiece positioned on the surface 26, or movable therealong, or otherwise successively positioned so that screws S, sequentially, may be entered into successive holes in said'means 12.

The power screwdriver 13, per se, is typical of such devices, conventionally comprising a motor 39 provided with an on and off switch 40 and having a driven arbor to which the bit 14 may be replaceably afiixed and, thereby, driven by the motor. A fixed extension 41 of said motor is fixedly held in the forwardly directed clamp 31 of the carriage frame 28. Said extension 41 mounts a forwardly directed bracket 42 that serves to mount the jaw-separating means 19.

The bit 14, in the usual way, is provided with an operating screw-driving end 43 which, shown as a wedge blade, may be typically formed for fitting recesses or socket while of various forms commonly used in screw heads.

As shown in FIG. 7, said bit 14 may be provided with an outer sleeve 44 which, as will be clear, serves to center the bit in the jaw means so the bit ends 43 are retained in alignment with the sockets in the screws, thereby enabling foolproof engagement between bit and screw during a driving operation. A compression spring 45 around the bit and around the sleeve 44 allows the driving end 43 to be extended into head engagement as the bit moves down in the jaws 17.

The means is shown as comprising the mentioned bracket 35, the forward portion of which is bifurcated to provide two transversely spaced ends 46, a vertical post 47 extending upwardly from each end 46 and each provided with a stop collar 48, a bridge piece 49 spanning across said posts 47 and slidingly engaged therewith, the mentioned spring 16 having its ends confined between the carriage frame 28 and the bridge piece 49, and a forward extension 50 on said bridge piece directed toward the axis of the bit 14. A spring 51, lighter than spring 16, is disposed between said bridge piece and a plate 52 afiixed to the bottom of the bracket 35, and provides a counter bias to the bias imposed by spring 16 on the means 15.

The jaw means 17 is shown as a pair of similar but opposite and elongated members 53 that when in nonseparated condition, as in FIG. 5, constitute a tubular part, split along the line 54, and include a vertical bore 55 that receives and has clearance for the bit 14. At their upper ends, the members 53 are each provided with an enlargement 56 that extends forwardly, the same having wedge faces 57 and 58 at the respective upper and lower portions of said enlargements. At the lower ends of the members 53, the same are so formed as to restrict the" size of the bore 55, said restriction 59 opening on a bore 60 at the extreme lower ends of said members and of a size, when the members 53 are in contact along the line 54, 'to be smaller than the heads of the screws S that are fed thereto. In said portion of the jaw means 17 in which the restriction 59 is provided, there is provided an opening 61 through which screws enter said restriction 59. As shown in FIG. 5, said opening 61 centers on the line of parting of the members 53, half of the opening being formed in each member. As seen in FIGS. 3, S and 6, a beveled seat 62 extends toward the bore 60.

The means 18 is shown as a pair of links 63 that extend from opposite sides of the extension 50 and from pivots 64 connecting said links to said extension in general parallelism to pivotal connections 65, one to enlargement 56 of each member 53 of the jaw means. Said links 63, while reasonably stiff, yet have sufficient resiliency so they will flex apart at their lower ends upon separating of the jaw members, as will become clear later.

The means 19 is shown as a vertical rod 66 that fixedly depends from the bracket 42 and preferably resides in the plane of the parting line of the jaw members 53. A collar 67, on the lower portion of the rod 66 below the lower end of the enlargements 56 of the jaw means 17, is provided with an upwardly directed wedge pin 68 that is in alignment with said parting line 54 so the same will enter the groove formed by the lower wedge faces 58, thereby spreading the members 53 apart, in the manner suggested in FIG. 6, when the carriage 11 is in raised retracted position, as in FIG. 1. A similar collar 69 on the upper portion of rod 66 above the upper end of the jaw means, is provided with a downwardly directed wedge pin 70 similarly aligned with the parting line 54 so the same will enter the groove formed by the upper wedge faces 57, thereby spreading the members 53 apart when the 11 is in the carriage powered position of FIG. 3.

The screw-feeding means is shown as a vibratory type of hopper 71 of conventional form and preferably disposed rearward of the stand 10. The same may be supported in any suitable manner. A sloping chute 72 is fed with screws displaced from said hopper, the same terminating at its lower end short of the jaw means and approximately at the level of the lower end of said jaw means when retracted as in FIG. 1. FIG. 4 shows several of the screws S in feed position in said chute. The screws are intercepted by the edge of a feed disc 73 that is located intermediate the length of the chute. When the disc 73 is rotated, a screw will enter a notch 74 in the edge thereof, and when re-rotated, the disc transports said screw from its initial position to the discharge side of the chute, from which it slides off the end 75 of the chute and into the opening 61 in the jaw means when said opening moves downwardly from the position of FIG. 1 toward the final screw-driving position of FIG. 3.

The means 21 for effecting this feed movement is shown as an arm 76 on the axis 77 of disc 73, and flexible means 78 guided in a fixed sheath 79' and extending to a connection, at 80, to the carriage frame 28. Thus, as the carriage moves down, the means 21 operates to enter a screw in the notch 74 of disc 73, and upon the upward movement of the carriage, said disc moves said screw to release position, from which it slides down the chute and through opening 61, as said opening moves upwardly from its extreme low position toward its upward retracted position.

It will be noted that the carriage 11 has a much greater movement than does the jaw means, the springs 16 and 51 compensating for the differences in the movement.

Operation Assuming that there is one or more screws in the chute 74 backed up by disc 73, and the member 12 is in position on the base 25, the handle 38 is pulled, causing the carriage 11 to move downwardly. The stronger spring 16 resists compression until the weaker spring 51 is substantially fully compressed and the bridge piece 49 reaches its limit of movement against the bracket 35. Thus, the bit 14 moves from a retracted position in the bore 55 of the jaw means 17 partly downwardly in said bore. During this part of the movement, the spring 16 may become partly compressed, in the ratio of its resistance to compression and that of the weaker spring 51. The full downward movement of the jaw means is thus completed when the means 15 is brought to a stop. At this time, the wedge pin 68 has released the jaw members so they may close.

Continued pull on the handle 38 causes the carriage to continue its downward movement so the bit 14 moves downwardly toward a screw that has been fed to the jaw means. However, before the blade 43 can encounter the screw, the wedge pin 70 again spreads the members 53, allowing said screw to settle down in the restricted portion 59 of the bore 55 before the blade encounters the kerf or socket in the screw head to drive the same under power of the operating motor 39. The spreading of the members may be effected against the bias of the spring of links 63 alone, or an O-ring 81 around the lower portions of the members 53 may exert such bias.

While the foregoing has illustrated and described what is now contemplated to be the best mode of carrying out the invention, the constructions are, of course, subject to modification without departing from the spirit and scope of the invention. Therefore, it is not desired to restrict the invention to the particular forms of construction illustrated and described, but to cover all modifications that may fall within the scope of the appended claims.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. An automatic screw-driving machine comprising:

(a) a base stand having a support surface for a member with holes for receiving screws,

(b) a carriage on said stand and vertically movable toward and from said surface and provided with a motor-driven screwdriver bit,

(c) an adjustable bracket on said stand located below and in spaced relation to the carriage,

(d) laterally separable jaw members coaxial with the bit and having a bore into which the driver end of the bit extends,

(e) means located in the space between the carriage and the adjustable bracket and connected to the mentioned jaw members,

(f) a spring between said means and the carriage and a second spring between the means and the bracket, said springs being compressible upon movement of the carriage toward the support surface to allow the bit to move downwardly in the bore of the jaw members during downward movement of the carriage,

(g) means to feed a screw into the lower end of said bore during retraction of the carriage under bias of said springs, and in position to be engaged by the screwdriver bit to be driven into a hole in the member on the support surface during the end of the downward movement of the carriage,

(h) means connecting said latter means to the carriage to operate the same, and

(i) means carried by the carriage to laterally separate the jaw members at both ends of the movement of the latter.

2. An automatic screw-driving machine according to claim 1 in which link means connect the resiliently mounted means and the jaw members, said link means having limited resilience allowing the same to be spread by the mentioned jaw member-separating means.

3. An automatic screw-driving machine according to claim 2 in which the resiliently mounted means is offset from the axis of the laterally separable jaw members, and the link means comprises two links, one connecting the latter means with each jaw member.

4. An automatic screw-driving machine according to claim 2 in which the spring between the carriage and the resiliently mounted means is stronger than the mentioned second spring, the latter, thereby, compressing during downward movement of the carriage to allow the bit to move down in the bore of the jaw members before the stronger Spring is compressed.

5. An automatic screw-driving machine according to claim 1 in which the screw-feeding means comprises:

(a) a sloping chute receptive of screws from a feed hopper, and

(b) a member in the path of movement of the screws in the chute to arrest the movement of screws and to sequentially transfer screws from the hopper side of the chute to the release side thereof for free fall to the end of the chute.

6. An automatic screw-driving machine according to claim 5 in which the means connected to the carriage is connected to said transfer member to move the latter back and forth between screw-arresting and screw-releasing positions as the jaw members correspondingly move between screw-driving and retracted positions.

7. An automatic screw-driving machine according to claim 1 in which the bore in the jaw members is oversize of the bit, a sleeve around the bit and slidingly fitting the mentioned bore, thereby to center the bit in the bore, the bit being normally retracted upwardly in said sleeve, and a spring around the bit and compressible, during screw-driving movement of the bit, to project the bit beyond the lower end of said sleeve and into engagement with the head of a screw in the lower end of the jaw members.

8. An automatic screw-driving machine according to claim 1, the jaw members having a separation line, and said line and the jaw-separating mean being coplanar, the latter means comprising: upper and lower wedge members to alternately enter between and spread the jaw members at the ends of vertical movement of the carriage.

9. An automatic screw-driving machine according to claim 8 in which the jaw members are provided with cooperating wedge faces between which the wedge members enter, said faces being provided on the upper and lower portions of enlargements at the upper ends of the jaw members.

References Cited UNITED STATES PATENTS 3,279,045 10/1966 Dixon 14432 GERALD A. DOST, Primary Examiner 

